Shiro Kawai:
> I implemented curly-infix notation in Gauche and stated to give
> it a try. And I can't help feeling c-exprs and s-exprs don't mix well. ...
> Here I pasted some code: https://gist.github.com/3502491
> I took exiting code that used some math (and I remember I wished
> to have had infix notation when I wrote them) and converted to C-exprs....
> I started itemizing why they don't mix, but before writing up
> a lenghthy email, I'd better check with you if I'm not doing it wrong.
I looked further at your pasted code (thanks for doing that). To be honest, I don't think it's terrible at all, I think it's an improvement from traditional s-expressions. From your description, and further looking, I'm guessing it's this kind of code you're unhappy about:
(define (S0 &#955; N)
(sum-ec (: n 1 N)
{&#955; * (exp (- {n * &#955;})) * (- {2 ^^ (ceiling (log n 2))}) * n}))
Again, I think this is a *BIG* improvement over traditional s-expressions.
I think as infix expressions get long they're less helpful. Since you can CHOOSE when to use them, you can skip it, which is actually an *advantage* over many other languages with built-in infix. Try this:
(define (S0 &#955; N)
(sum-ec (: n 1 N)
(*
&#955;
(exp (- {n * &#955;}))
(- {2 ^^ (ceiling (log n 2))})
n)))
Now that said, its inability to handle stuff of the form f(...), such as -(...), is a big drawback. We could add support for neoteric-expressions inside {...} to resolve that; it's an easy spec change, and that specification is mature. So let's see what that would do:
(define (S0 &#955; N)
(sum-ec (: n 1 N)
{&#955; * exp(-({n * &#955;})) * -({2 ^^ ceiling(log(n 2))}) * n}))
That's better. Again, kind of long for infix; try this:
(define (S0 &#955; N)
(sum-ec (: n 1 N)
(*
&#955;
exp(-{n * &#955;})
-{2 ^^ ceiling(log(n 2))}
n)))
If you don't like the mixing of () and {}, well, we intentionally designed it so that when you have 0 and 1 parameters you can use either. That becomes (back to few lines):
(define (S0 &#955; N)
(sum-ec (: n 1 N)
{&#955; * exp{-{{n * &#955;}}} * -{{2 ^^ ceiling(log(n 2))}} * n}))
This compares favorably with full neoteric-expressions, which allow the use of f(x) for (f x) ANYWHERE:
define( S0(&#955; N)
sum-ec( (: n 1 N)
{&#955; * exp{-{{n * &#955;}}} * -{{2 ^^ ceiling(log(n 2))}} * n}))
Well, those are a lot of options. In *practice*, what I would do is switch to a NON-infix form once the expression gets to be more than half a line with complex expressions inside them (as shown above). So with curly-infix ONLY I'd do this (as shown above):
(define (S0 &#955; N)
(sum-ec (: n 1 N)
(*
&#955;
(exp (- {n * &#955;}))
(- {2 ^^ (ceiling (log n 2))})
n)))
--- David A. Wheeler